WE LIVE IN A WORLD OF INSTANT GRATIFICATION. GROWING CRYSTALS TEACHES KIDS THAT YOU CAN’T RUSH NATURE. ALTHOUGH CRYSTALS CAN TAKE WEEKS TO GROW, SUCH PROJECTS AS MAKING ROCK CANDY CAN HAVE A GREAT PAYOFF AT THE END.

Crystals are geometric grids of atoms. Imagine a three-dimensional chain-link fence and you’ll get the picture. From the salt crystals on your table to the silicon crystals that make up semiconductors, LED displays, and solar cells, we depend on these ordered networks of molecules to enhance our lives.

In this unit, you’ll use supersaturated solutions to grow two types of crystals: alum and sugar. All of the ingredients can be picked up at your local grocery store, if you don’t already have them on hand.

CREATE SPARKLING GEODES BY USING ALUM POWDER AND EGGSHELLS.

  3 whole raw eggs

  Serrated knife

  Small paintbrush or cotton swab

  Glue

  2 cups (475 ml) water

  Small pot, to boil the water

  Food coloring (optional)

STEP 2. Apply a thin layer of glue to the inside of an eggshell, using a paintbrush or cotton swab. (Fig. 1) Sprinkle alum powder on the wet glue and let your eggs dry overnight. (Fig. 2)

Fig. 1: Paint the inside of an eggshell with glue.

Fig. 2: Sprinkle alum crystals on the wet glue.

STEP 3: Dissolve the 3/4 cup (160 g) of alum in the water by boiling the mixture in a small pot. This step requires adult supervision. Make sure all the alum dissolves (it may still look a little cloudy) and let the solution cool. This is your supersaturated alum solution.

Fig. 3: Add the alum to the water and boil to dissolve.

STEP 4: When the solution is cool enough to be safely handled, gently immerse your eggshell in the alum solution. For color, you can add a large squirt of food coloring. (Fig. 4)

Fig. 4: Submerge the “seeded” eggshell in the cool alum solution.

STEP 5: Let your project sit undisturbed to grow crystals.

STEP 6: After three days, gently remove your object from the alum solution and let it dry. (Fig. 5)

Fig. 5: Remove your eggshell from the alum solution and dry.

NOTE: Alum can be found in the spice section of a grocery store or supermarket. Usually four or five small jars will do the trick.

GROW COLORFUL, DELICIOUS SUGAR CRYSTALS ON A STICK.

  2 cups (470 ml) water

  Cake-pop sticks or wooden skewers

  Medium-size pot, to boil the water

  Glass containers

  Food coloring

PROTOCOL

STEP 1: Dip one end of the cake-pop sticks or wooden skewers in water and then roll them in the sugar. The sugar should cover 2 to 3 inches (5 to 7.5 cm) of the sticks. Let them dry completely. These are the seeds for the sugar crystal growth. (Fig. 1)

Fig. 1: Roll the ends of the sticks in sugar.

STEP 2: Boil the 2 cups of water and the 5 cups sugar in a medium-size pot until the sugar is dissolved as much as possible. It should look like syrup. Once cool, this is your supersaturated sugar solution.

STEP 3: Let the syrup sit until it is no longer hot, and pour into glass containers. Add food coloring and stir. (Fig. 2)

Fig. 2: Add food coloring to syrup and stir.

STEP 4: When the colored syrup has cooled to room temperature, set the sugary end of the sugar-seeded cake-pop sticks or skewers into the syrup and let them sit for about a week. Gently move the sticks around occasionally, so they don’t stick to the crystals in the bottom of the glass. If the glass container gets too full of crystals, pour the syrup into a new container and move your stick into the clear syrup to grow more crystals.

STEP 5: When the rock candy is done, drain the excess syrup and let the sticks dry. Look at them under a magnifying glass for a close-up look. (Fig. 3)

Fig. 3: Remove the candy from the syrup.

STEP 6: Bon appétit!